Stripe Helical Magnetism and Two Regimes of Anomalous Hall Effect in NdAlGe

Recently, the discovery of helical magnetism induced by Weyl-mediated exchange interactions in NdAlSi, a Weyl semimetal breaking both inversion and time-reversal symmetries, provides a new example of topological magnetism contributed by Weyl nodes. However, it remains a question that whether or not the topological magnetism persists in its sibling compound NdAlGe. In addition, with the presence of topological magnetism, it is not clear how Weyl nodes may affect the transport properties of these materials. Here, we provide conclusive evidence that NdAlGe also hosts the same type of topological magnetism as NdAlSi. The transport properties, however, differ greatly between NdAlSi and NdAlGe in carrier concentrations, mobility, and anomalous Hall effect (AHE). In particular, we did not find a clear sign of AHE in NdAlSi, but we observe two regimes of AHE in NdAlGe, governed by intrinsic Berry curvature and extrinsic disorders/spin fluctuations, respectively. Our study suggests that compared to topological magnetism, transport properties including AHE in Weyl semimetals are generally involved with more material specifics and more susceptible to disorders.